In my opinion with my own testing 8x1.3 Flat pistons are the ticket. JB wicked weekend setup is what I run. 3x2.1 wont give the pack necessary taking in consideration the weight of truggy. 700f 600r or 650f 550r with colder weather. I ran rear HRC this past weekend on my ET48.3 and they were $$$. Truck was over rotating on corners mid to exit and the HRC hubs locked in the rear. I was able to push it harder on exit.